Our guy does that, we fixed the problem by defining a place where he can dig (his bed and his crate). We even join in some times and make it a family game.
When he was little and dug other places we would pick him up and put him either in his kennel (door open) or his bed to dig. Now when he is just doing it to be a brat he gets one chance to be relocated and then I get out the bitter apple. Not to spray on the spot, I spray it in the air around him he finds it extremely unpleasant.
Usually I keep a tiny 3oz spray bottle full for correction purposes. Be careful though do not spray directly into the face that could be dangerous. I usually mist around him like you would do with perfume. Or if he is particularly unlucky and has his mouth open I do it from the side so it goes directly into his mouth.
After one or two "No" :spray: he gets the point. Oh ya we don't really have that problem any more.